1. Field of the Invention
This invention relates to a compact, relatively low cost, energy-saving electronic ballast that is particularly useful for efficiently driving a fluorescent tube or a compact fluorescent lamp. The ballast is characterized by a high power factor, low total harmonic distortion and minimal radio frequency interference and is adapted to be used with compatible tubes and lamps from different manufacturing sources. A protection circuit is connected to the ballast to prevent damage thereto in the event that the tube or lamp is defective or disconnected from the ballast or subjected to abnormal operating conditions.
2. Background Art
Fluorescent tube and compact fluorescent lamp assemblies are well known lighting devices. The fluorescent tube assembly includes a tube and a separate electronic ballast or adapter to drive the tube. In the case of the compact fluorescent lamp assembly, a lamp and ballast are combined as an integrated unit.
The conventional ballast that is associated with the fluorescent tube assembly is typically heavy and large. Moreover, such a ballast is not very energy efficient and is characterized by a low power factor. The conventional ballast associated with the compact fluorescent lamp assembly is also characterized by a low power factor, unless size is sacrificed. Such a ballast is also characterized by total harmonic distortion which, in many cases, is not in full compliance with government regulations. Because the compact lamp and electronic ballast are integrated, the entire lighting assembly must be discarded when the lamp is damaged or reaches the end of its life. The foregoing results in waste and inefficient use of materials, particularly in view of the fact that the ballast is more costly to manufacture than the lamp and commonly has a longer expected life span.
Ballasts are also known to fail because of certain failures in the fluorescent tube or lamp. Consequently, the life of the ballast is reduced and the frequency of replacement is increased, whereby operating costs are correspondingly increased. Such failures to the ballast may occur if power is applied when the tube (i.e. load) is removed from the ballast or when an incorrect or defective tube is connected to the ballast or the tube is subjected to either a transient voltage surge or a high ambient temperature that alters the electrical characteristics thereof.
It would therefore be desirable to overcome the aforementioned shortcomings to fluorescent lighting devices by providing a lightweight, compact, energy efficient electronic ballast that would have low total harmonic distortion, minimum radio frequency interference, and a high power factor (e.g. 0.9 or higher). Moreover, it would be desirable that the ballast be detachable from the fluorescent lamp so that the lamp can be replaced without the necessity of scrapping the ballast. In addition, the ballast must comply with all government regulations and be compatible with fluorescent tubes and lamps that are produced by different manufacturers. Furthermore, it would be desirable to have a protection circuit connected to the ballast to reduce failures thereof as a consequence of certain failures in the tube or lamp.